There exists a requirement for antennas on portable radio equipment to have the facility of being operational when retracted into the set and of offering improved performance when extended, or to be capable of being laid down alongside the equipment for transport or convenience, or to achieve a suitable angle for operation.
Conventionally this is achieved by a mechanical telescopic rod or a fixed rod which slides out, or by a pivot arrangement, created by a "tongue and slot" in metal with a method of maintaining friction.
Both these methods require a mechanical connection to the rod in order to provide the electrical "joint" to the radio.
This mechanical interface is prone to problems from two areas:
1) The connection point is subject to wear resulting in intermittent contact. PA1 2) It is very difficult to maintain a consistent and repeatable joint to allow optimisation of the various tuning components within the radio.